Exhaust gas recirculation valve assembly

Abstract

An engine exhaust gas recirculating (EGR) valve assembly that maintains the EGR valve in the position to which it is actuated by means of a rolling diaphragm air bleed device that alternately covers and uncovers an atmospheric vent opening until an equilibrium position is maintained.

I claim: 
     
       1. An engine exhaust gas recirculating (EGR) valve assembly, comprising in combination, a duct connecting engine exhaust gases to the engine intake manifold, an (EGR) valve movable into and out of the duct to block or permit flow of gases through the duct, a spring biasing the (EGR) valve into the duct to a closed position, fluid pressure actuated force means connected to the (EGR) valve for moving it to an open position against the forces of gases and manifold pressure acting in the duct on the valve, means connecting a source of varying pressure to the force means to actuate the same, a movable atmospheric bleed device movable to decay the pressure from the source below a level operative to effect opening of the (EGR) valve, and control means operably connected to the bleed device to move the same to control the decay of source pressure force, the force means including a servo having a diaphragm dividing the servo into an atmospheric pressure chamber on one side and a variable fluid pressure chamber on the other side, a valve stem connected to the (EGR) valve and to the diaphragm and projecting through the diaphragm from one side to the other, the bleed device including bypass passage means in the stem having an outlet opening into each chamber for decaying the pressure in one chamber to the level of the pressure in the other chamber, and rollable flexible seal means movable by the control means between a first position uncovering the outlet in one chamber to expose the latter outlet to atmospheric pressure to equalize the level of the pressures in the chambers to thereby permit movement of the diaphragm in a valve closing direction by the spring or movable to a second position to cover the latter outlet to permit a change in the force level of the pressure in the variable pressure chamber to effect an (EGR) valve opening movement of the diaphragm, the latter movement of the diaphragm moving the stem relative to the seal means to again uncover the latter outlet and again effect the movement of the diaphragm and stem and (EGR) valve in a valve closing direction, the valve moving back and forth until an equilibrium position is attained for each movement of the control means. 
     
     
       2. An (EGR) valve assembly as in claim 1, including an additional outlet to the bypass passage located in the atmospheric chamber adjacent the first named outlet, the flexible seal means forming a fluid pressure chamber located over the additional outlet to be pressurized by the variable pressure, the first named outlet being sealed by the pressurized rolling seal means as it is moved by the control means to cover the outlet. 
     
     
       3. An engine exhaust gas recirculating (EGR) valve assembly, comprising in combination, a duct connecting engine exhaust gases to the engine intake manifold, an (EGR) valve movable into and out of the duct to block or permit flow of gases through the duct, a spring biasing the (EGR) valve into the duct to a closed position, fluid pressure actuated force means connected to the (EGR) valve for moving it to an open position against the forces of gases and manifold pressure acting in the duct on the valve, conduit means connecting a source of varying pressure to the force means to actuate the same, a movable atmospheric bleed device movable to decay the pressure from the source below a level operative to effect opening of the (EGR) valve, and control means operably connected to the bleed device to move the same to control the decay of source pressure force, the force means including a servo having a diaphragm dividing the servo into an atmospheric pressure chamber on one side and a variable fluid pressure chamber on the other side, passage means extending through the diaphragm providing communication of pressures on opposite sides of the diaphragm, the bleed device including rollable flexible seal means rollable by the control means between a first position uncovering the passage means in one chamber to expose the passage means to atmospheric pressure to equalize the level of the pressures in the chambers to thereby permit movement of the diaphragm in an (EGR) valve closing direction by the spring or to a second position to cover and seal the passage means in the one chamber to permit a change in the force level of the pressure in the variable pressure chamber to effect an (EGR) valve opening movement of the diaphragm, the latter movement of the diaphragm moving the stem relative to the slide valve means to again uncover the passage means and again effect the movement of the diaphragm and stem and (EGR) valve in a valve closing direction, the valve moving back and forth until an equilibrium position is attained for each movement of the control means, the conduit means having a flow area less than the flow area of the passage means. 
     
     
       4. An (EGR) valve assembly as in claim 3, the passage means including an outlet in the atmospheric pressure chamber surrounded by the seal means to form a flexible pressure chamber that rolls over the passage means in response to the control means to seal the passage means at that point from communiction with the atmospheric pressure chamber. 
     
     
       5. An (EGR) valve assembly as in claim 3, including electrical means connected to the control means for operating the same in response to an electrical input signal from the engine. 
     
     
       6. An (EGR) valve assembly as in claim 3, including second fluid pressure operating means connected to the control means and operable in response to movement of a carburetor throttle valve to move the rollable seal means. 
     
     
       7. An (EGR) valve assembly as in claim 6, the second fluid pressure operated means comprising a pair of interconnected pneumatically operated pistons for transmitting the force and movement of one to the other, and linkage means between the throttle valve and one of the pneumatic pistons for directly actuating the same upon movement of the throttle valve. 
     
     
       8. An (EGR) valve assembly as in claim 3, the passage means being formed in a valve stem secured to the (EGR) valve and diaphragm and projecting through the diaphragm with an outlet to the passage means on each side of the diaphragm, the rollable seal means comprising a rollable flexible diaphragm having one portion secured to the control means and an opposite portion secured to the valve stem straddling an outlet to seal the same, an additional outlet from the passage means, the additional outlet being in the chamber defined by the seal means adapted to be covered and uncovered by the rolling movement of the seal means to alternatively expose the additional outlet and passage means to the chamber pressure or cover the additonal outlet to permit the buildup of pressure in the other chamber, the other chamber pressure pressurizing the seal means upon covering of the additional outlet to seal the additional outlet. 
     
     
       9. An (EGR) valve assembly as in claim 8 the control means including an open end cylindrical-like member receiving the seal means therein and to which the seal means is secured.